1. Field of the Invention
The present invention relates generally to an interconnection, or “tap,” point in a fiber optic communications network. More specifically, the invention is a fiber optic distribution cable having an adjustable tap point comprising at least one connector port attached by a tether to a mid-span access location of the fiber optic distribution cable, wherein the tether provides a length of slack cable to permit the connector port to be positioned at a desired location in the fiber optic communications network.
2. Description of the Related Art
Optical fiber is increasingly being used for a variety of broadband communications including voice, video and data transmissions. As a result of the increasing demand for broadband communications, fiber optic networks typically include a large number of mid-span access locations at which one or more optical fibers are terminated from a distribution cable and interconnected with a branch cable or a drop cable. The mid-span access locations provide an interconnection point, also referred to herein as a “tap” point, from the distribution cable leading to another network distribution or termination point, or from the distribution cable leading directly to an end user, commonly referred to as a subscriber, thereby extending an “all optical” communications network closer to the subscriber. In this regard, fiber optic networks are being developed that deliver “fiber-to-the-curb” (FTTC), “fiber-to-the-business” (FTTB), “fiber-to-the-home”(FTTH), or “fiber-to-the-premises” (FTTP), referred to generically as “FTTx.” Based on the large number of mid-span access locations and the unique demands of optical fibers and optical connections, a tap point is needed for providing access to terminated optical fibers in an FTTx network. More particularly, a tap point is needed that is capable of being adjustably positioned along the length of a distribution cable, or positioned away from the distribution cable in order to mitigate span length measurement differences that are encountered when installing a fiber optic distribution cable having predetermined mid-span access locations in a fiber optic communications network.
In one example of a fiber optic communications network, one or more drop cables are interconnected with a distribution cable at a tap point comprising a mid-span access location. Substantial expertise and experience are required to configure the optical connections in the field. In particular, it is often difficult to identify a particular optical fiber of the distribution cable to be optically connected with an optical fiber of a drop cable. Once identified, the optical fiber of the distribution cable is typically joined directly to the optical fiber of the drop cable at the mid-span access location using conventional splicing techniques, such as fusion splicing. In other instances, the optical fiber of the distribution cable and the optical fiber of the drop cable are first spliced to a short length of optical fiber having an optical connector mounted on the other end, which is generally referred to in the art as a “pigtail.” The pigtails are then routed to opposite sides of a connector adapter sleeve to interconnect the drop cable with the distribution cable. In either case, the process of configuring the mid-span access location is not only time consuming, but frequently must be accomplished by a highly skilled field technician at significant cost and under field working conditions that are less than ideal. In situations in which a mid-span access location is enclosed within a conventional splice closure, reconfiguring optical connections within the splice closure is especially difficult, based in part on the relatively inaccessible location of the closure, the limited workspace available within the closure, and the inability to readily remove the closure from the distribution cable. Further, once the spliced optical connections are made, it is labor intensive, and therefore relatively costly, to reconfigure the optical connections or to add additional optical connections.
In order to reduce installation costs by permitting less experienced and less skilled technicians to make optical connections and to reconfigure optical connections at mid-span access locations in the field, communications service providers are increasingly pre-engineering new fiber optic networks and demanding factory-prepared interconnection solutions, commonly referred to as “plug-and-play” type systems. There are currently several methods to build a distribution cable assembly for economical deployment and field installation. In one example, the distances between desired network distribution or termination points (i.e., tap points) are measured with great accuracy and a factory-prepared distribution cable assembly is built with mid-span access locations positioned precisely at the desired tap points. However, in this instance the length of the distribution cable between mid-span access locations must be exact, and the deployment of the distribution cable must be performed accurately so that no extra cable length is used between the tap points. If extra length of distribution cable is used, the incorrect placement of even one mid-span access location will have a compounding effect on the position of each downstream mid-span access location. As a result, all downstream mid-span access locations will be out of position and the length of distribution cable will come up short at the end of the cable run. Obviously, measuring the absolute distances between mid-span access locations and building a distribution cable assembly with accurate distances between mid-span access locations is a difficult undertaking. Furthermore, any error in the manufacturing process may result in the entire distribution cable assembly being unusable, and therefore scrapped. Alternatively, an excess length of cable (i.e., slack) may be intentionally built into the distribution cable at each mid-span access location to insure that the tap point can always be positioned in the field at exactly the desired location. The obvious drawbacks with such a distribution cable assembly are the cost associated with the excess lengths of the cable and the associated need to store the cable slack in an aesthetic and practical manner.
In addition to the difficulties associated with manufacturing a distribution cable assembly having the tap points in the pre-engineered locations, there are also problems encountered with using conventional components to optically connect the optical fibers of the distribution cable with optical fibers of a branch cable or drop cable at the mid-span access locations. For example, rigid enclosures are typically used to protect the section of the distribution cable that must be exposed to access the appropriate optical fibers and the splices. Distribution cables provided with conventional enclosures tend to be large in size and inflexible, and thus, unable to satisfy common deployment constraints, such as being wound onto a reel, deployed through conduits having a relatively small inner diameter or significant bends, or deployed through conventional aerial lashing equipment, such as sheaves and rollers. Furthermore, such enclosures are often structurally complex and difficult to install.
Accordingly, there is a specific and unresolved need for a factory-prepared, fiber optic distribution cable having an adjustable tap point that mitigates the difference between the pre-engineered span length distance and the actual span length distance following installation of the distribution cable. Further, there is a need for a fiber optic distribution cable including at least one predetermined mid-span access location for providing access to at least one preterminated optical fiber and a tether assembly including at least one connector port for interconnecting the preterminated optical fiber with an optical fiber of a branch cable or drop cable at a desired location along the length of the distribution cable. To accommodate any installation environment, the tap point preferably has a small diameter and is flexible enough to be wound onto a reel, deployed through a conduit having a relatively small inner diameter or significant bends, or deployed using conventional aerial lashing equipment. In addition, there is a specific and unresolved need for a factory-prepared fiber optic distribution cable that does not require a highly skilled field technician or extensive field labor to interconnect optical fibers of the distribution cable with optical fibers of a branch cable or drop cable.